Facebook use fell during that period from 54 percent of total at-work social networking to 37 percent, the report found. Facebook is still the most popular social network for people to use on the job, but Twitter and other services are quickly catching up.

Twitter jumped from 11 percent of workday social networking use in 2011 to 21 percent this year. Tumblr traffic increased 10-fold over the same period, making up 10 percent of workplace social networking, and Pinterest sprang onto the scene, now accounting for 1 percent.

Yet despite the rapid emergence of new social networks, the overall amount of social networking at the workplace hasn’t increased since last year, the study showed. The total traffic from social networking applications remains at a mere 1 percent of total in-office bandwidth consumption.

The report’s findings may confirm fears among some business owners who worry employees are increasingly wasting time on the Web. The study’s authors said that, based on the number of applications that appeared on each organization's network, “a large portion” of at-work social networking and video viewing appeared to be “for personal use.”

Still, some executives argue that the line between “personal” and “work-related” Internet activity is blurring as employees increasingly use social networks to market products, monitor competitors and communicate with customers.

“I don't see corporate social media as a problem,” Nihal Mehta, the CEO of digital marketing firm Local Response, told The Huffington Post in January. “The more active folks are, and the more followers they gain online, the better they can act as ambassadors for the brand."

Facebook may make it easier for some employees to do their jobs, but it's difficult to see how watching cute kitten clips on YouTube boosts productivity.

And it turns out streaming video is the fastest-growing segment of in-office traffic. Streaming video increased this year more than three-fold, from 4 percent of total workplace bandwidth use to 13 percent. YouTube was the most significant contributor, accounting for 3.8 percent of total bandwidth consumption.

The study also noted that no large video events, like the Olympics, occurred during the period analyzed, something that could have otherwise explained the streaming video spike.